Re: [RFC v3][PATCH 0/2] Make ftrace able to trace function return

[fche@redhat.com (Frank Ch. Eigler)]

Frederic Weisbecker <fweisbec@gmail.com> writes:

> This patchset adds the ability for ftrace to trace the function even
> on call time and on return time. So we can now measure the time of
> execution of the most part of the functions inside the kernel with
> ftrace. [...]

By the way, one extra complication you may need to deal with, beyond
normal retprobes, is that by the time dyn-ftrace gets hold of the
function entry, some part of the function prologue will have been
executed.  Because the mcount call/sequence is not the first
instruction in the function body, is there a risk that the call frame
cannot be reliably modified because of interference from those first
few other instructions?  Maybe on some architectures/optimization
levels?

- FChE